JPH06150901A - Combined secondary battery - Google Patents

Abstract

PURPOSE:To properly maintain inherent lifetime of a combined secondary battery by preventing occurrence of overcharge at a charging process and overdischarge at a discharging process prior to a charging process. CONSTITUTION:Silicon diodes D1 to D5, load resistors R1 to R5 and switches S1 to S5 are respectively connected to nickel-cadmium cells E1 to E5 as a series circuit, and a combined secondary battery is thereby constituted. As a result, when the switches S1 to S5 are respectively turned on, each of the nickel- cadmium cells E1 to E5 is independently discharged, and this discharging process ends, when the residual capacity thereof comes near the offset voltage values of the silicon diodes D1 to D5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rechargeable battery pack which is constructed by connecting a plurality of single secondary batteries such as nickel-cadmium batteries (hereinafter referred to as NiCd batteries) and is used as a power source for portable video cameras and the like. It is about.

[0002]

2. Description of the Related Art In recent years, in video cameras and the like, a camera and a recorder have been integrated and the size and weight have been reduced.
It is becoming popular as a portable type that can be easily carried by general users.

In such a portable video camera or the like, from the viewpoint of current capacity, running cost, etc., a secondary battery such as a nickel-cadmium battery is used rather than a primary battery such as a manganese battery or an alkaline battery. A rechargeable battery is used as a power source for carrying.

FIGS. 5A and 5B are perspective views showing an example of a power pack of a rechargeable battery used in a portable video camera. As shown in these drawings, for example, five NiCd cells E _{1 to} E ₅ are built in the power pack 1 including a housing upper portion 1 a and a housing lower portion 1 b. As shown in the circuit diagram of the rechargeable battery of FIG. 6, these NiCd cells E _{1 to} E ₅ are connected in series inside the power pack 1 shown by the broken line so that a predetermined voltage can be obtained as an assembled battery. And the terminal T is connected to the negative electrode of the NiCd cell E _1.
1 , the terminal T ₂ is connected to the positive electrode of the NiCd cell E ₅ to form a rechargeable battery pack.

[0005] These terminals T ₁ and T ₂ are actually provided so as to be exposed to the housing lower part 1b which is not shown, predetermined power pack 1 shown in FIGS. 5 (a) to a video camera By mounting by the method, the terminals T ₁ and T ₂ on the side of the power pack 1 come into contact with the terminals corresponding to the terminals T ₁ and T ₂ provided on the side of the video camera body, and power is supplied to the video camera. You can do it.

When the charging capacity of the rechargeable battery pack decreases due to the use time of the video camera or self-discharge, the terminals T ₁ and T ₂ are attached by mounting the power pack 1 on a charger (not shown). And terminal T provided on the charger side
_1, T ₂ terminals corresponding contacts in the terminal T ₁ and T ₂
Charging current is supplied in the meantime to perform charging, and the rechargeable battery can be repeatedly used.

FIG. 7 is a graph showing the charging characteristics of a nickel-cadmium battery, in which the vertical axis represents the voltage of the nickel-cadmium battery and the horizontal axis represents the charge amount. NiCd cell is point C in the figure
As shown in, the voltage has a characteristic that the voltage suddenly rises when the charged amount is around 120% and then drops. Therefore, when charging the rechargeable battery pack using NiCd cells with the charger, the voltage of the charger suddenly rises at point C.
Is detected to end the charging, thereby preventing overcharging.

By the way, the nickel-cadmium battery used in the above-mentioned rechargeable battery pack has a property that the battery capacity gradually decreases each time charging / discharging is repeated.
It is considered that the actual average life of the NiCd cell is around 00 times or more.

The charging capacity of a nickel-cadmium battery is reduced by supplying power to a load or the like, and the charging capacity is relatively quickly reduced even when it is not connected to a device due to a self-discharge phenomenon. It is known. Also,
Even in the same type of NiCd cell, the self-discharge characteristics are not uniform because there are some differences in the individual characteristics.

FIG. 8 is a graph showing an example of the self-discharge characteristics of two NiCd cells of the same type, which are shown by curves A and B, respectively. The vertical axis represents the remaining capacity of the battery and the horizontal axis represents the storage period of the battery. As is clear from this graph, even in the NiCd cells of the same type, a difference of 10% or more has already occurred in the remaining capacity two months after full charge.

That is, even in a rechargeable battery pack in which a plurality of NiCd cells are connected in series, the discharge characteristics of the individual NiCd cells may be different from each other. At the time of decrease, the state of charge of the individual NiCd cells varies.

[0012]

Therefore, when the rechargeable battery pack having the above-mentioned individual nickel-cadmium cells with varying remaining capacities is charged by the charger, the nickel-cadmium cells described in the graph of FIG. 7 are used. Since the characteristics of the battery are affected and the curve around the point C cannot be obtained correctly, the detection operation of the charger does not work properly and the operation for ending the charging is delayed.
As a result, among the rechargeable battery packs, the nickel cadmium battery having the characteristic of having a relatively large remaining capacity is overcharged at the end of charging.

Repeating such overcharging deteriorates the characteristics of the NiCd cell and shortens the life of the NiCd cell. For this reason, among the rechargeable battery packs, the nickel cadmium single battery having the characteristic of having a large remaining capacity has its characteristics rapidly deteriorated and its life shortened.

In the rechargeable battery pack, the comprehensive characteristics and life of the rechargeable battery pack are determined according to the unit battery having the most deteriorated characteristics among the battery cells constituting the battery pack. However, since it is difficult to construct an assembled battery while avoiding variations in the discharge characteristics of the unit cells, the life of the rechargeable assembled battery has become shorter than it actually is.

For this reason, in the charger, when charging the assembled battery, for example, before charging, the terminals T ₁ and T ₂ are connected on the charger side through a load resistor having a predetermined value for discharging, and then the charging operation is performed. Are configured to do.

However, even if the battery is discharged by the above-mentioned charger, the variation in the remaining capacity of each NiCd cell may not be solved, and when charging is repeated for such an assembled battery, Again, there is a problem in that overcharging is repeated for a specific unit cell, which shortens the life of the assembled battery.

Further, when the battery is charged with the remaining capacity remaining, it cannot be charged with a predetermined electric power. Therefore, in the case of a secondary battery in which such a battery is incorporated, the assembled battery after charging is charged. There is also a problem that the battery cannot drive the video camera or the like for a predetermined time.

[0018]

SUMMARY OF THE INVENTION In order to solve these problems described above, the present invention aims to eliminate individual variations in the remaining capacity of a secondary battery configured as a rechargeable battery pack before charging. Is intended to be discharged. Therefore, one terminal is provided between each of the plurality of single secondary batteries connected in series, and each single secondary battery can be individually discharged between these terminals to form a set secondary battery. I decided. For each of a plurality of single secondary batteries connected in series, a load resistance and a switch for discharge are connected in series to form a set secondary battery, or a diode element and a load for discharge are connected. A resistor and a switch were connected in series to form a secondary battery pack.

[0019]

[Operation] In the rechargeable battery pack, one terminal is provided between each of the plurality of single secondary batteries connected in series, and a load resistor is connected between these terminals on the charger side before charging. Discharge. Alternatively, for each of a plurality of single secondary batteries, a load resistance for discharging, a switch, and a diode element are connected in series to configure a secondary battery, and each switch is turned on at the charger side during charging. If it can be turned on / off, each single secondary battery can be independently discharged.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit diagram of FIG. 1 shows an embodiment of the assembled secondary battery of the present invention, and shows the inside of the power pack 1 of the rechargeable battery of the portable video camera shown in FIG. As shown in the figure, the five NiCd cells E _{1 to} E ₅ built in the power pack 1 shown by broken lines are connected in series. The terminal T ₁ is connected to the negative electrode of the nickel-cadmium battery cells E ₁ is a nickel-cadmium battery cells E ₅
The terminal T ₂ is connected to the positive electrode of, and these terminals T ₁ and T ₂ are provided so as to be exposed to the power pack 1. And
Supply of power to the portable video camera and charging by the charger are performed via terminals T ₁ and T ₂ .

Further, in the present embodiment, the discharge terminal T ₃
~ T ₆ are provided. As shown in the figure, one discharge terminal is connected between each NiCd unit cell and one NiCd unit cell, and the connected discharge terminals T _{3 to} T ₆ are connected.
Are exposed and provided in the power pack 1.

Regarding the charger, the terminals T ₁ -terminal T ₃ , terminal T ₃ -terminal T ₄ , terminal T ₄ -terminal T ₅ , terminal T ₅ -terminal T ₆ , terminal T of the rechargeable battery to be mounted are attached. A load resistance having a predetermined value can be connected to each of the ₆ -terminals T ₂ .

Therefore, when charging the rechargeable battery according to the present embodiment, after the rechargeable battery is mounted on the charger, for example, the user discharges the charger or the rechargeable battery. Connect the load resistor between the terminals of the rechargeable battery by operating the button for the battery. Alternatively, this may be configured to be performed automatically.

As described above, by connecting the resistors between the terminals of the rechargeable battery, the five nickel cadmium cells E _{1 to} E are connected.
Each of ₅ will be discharged independently, and will be discharged from the NiCd cell with a large remaining capacity. By performing such a discharging operation for a predetermined time, the variation in the remaining capacity of each NiCd unit cell after discharging is eliminated and becomes constant.

After the rechargeable battery is discharged in this way, the load resistance connected between the terminals is released and the charging current is supplied between the terminals T ₁ and T ₂ to perform the charging operation. I do. At this time, since the variation in the charging capacity of each NiCd cell is eliminated and becomes constant, the charging characteristics shown in FIG. 7 are obtained correctly, and the detection of point C by the charger side also operates normally. Therefore, it is possible to avoid overcharging the specific NiCd cell.

Since each of the Ni-Cd cells E _{1 to} E ₅ is discharged so that the remaining capacity becomes 0 before charging, 100% of electric power can be stored by the subsequent charging, and the assembled battery As a result, the charging capacity will increase.

The circuit diagram of FIG. 2 shows another embodiment of the present invention, and shows the inside of the power pack 1 of the rechargeable battery of the portable video camera shown in FIG. 5, as in FIG. Further, the same parts as those in FIG.

In the present embodiment, inside the rechargeable battery, that is, the inside of the power pack 1, the Ni-Cd cells E _{1 to} E are provided.
Load resistor R ₁ to R ₅ of the predetermined value for each of the _5, it connects the switch S ₁ to S ₅ in series. That is, for the NiCd cell E ₁ , the load resistance R ₁ is connected to the positive electrode of the NiCd cell E ₁ , and is connected to the negative electrode of the NiCd cell E ₁ via the switch S ₁ . Then, configured as a rechargeable battery likewise load resistors for each R ₂ to R ₅ and the switch S ₂ to S ₅ of NiCd battery cells E ₂ to E ₅ are connected, respectively. Further, the charger for charging the rechargeable battery is provided with, for example, a plunger or the like that enables the switches S _{1 to} S ₅ to be turned on / off at the same time.

When charging the rechargeable battery constructed as described above, the switch S ₁ inside the rechargeable battery is first attached by the plunger on the charger side after mounting the rechargeable battery on the charger. ~ Turn on S ₅ . Since the current path becomes the same as in the case of FIG. 1 by the above operation, discharge is started for each of the NiCd cells E _{2 to} E ₅ , and the remaining capacity of each NiCd cell is constant at the end of charging after a predetermined time. It becomes a state. This After plunger and off the switch S ₁ to S ₅ of the internal rechargeable battery, by performing charging in the same manner as in Example 1, not that a particular nickel-cadmium battery cells becomes over-charged.

The circuit diagram of FIG. 3 shows still another embodiment of the present invention, and like the embodiment shown in FIGS. 1 and 2, the power pack 1 for the rechargeable battery of the portable video camera shown in FIG. It is supposed to be internal. Further, the same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, in addition to the load resistance and switch described in the embodiment of FIG.
Silicon diodes D _{1 to} D ₅ are further connected in series to each of _{1 to} E ₅ .

That is, for the NiCd cell E ₁ ,
A silicon diode D ₁ is connected to the positive electrode of the Ni-Cd battery cell E ₁ , and is connected to the negative electrode of the Ni-Cd battery cell E ₁ via a load resistor R ₁ and a switch S ₁ . Then, nickel-cadmium battery cells E ₂ to E load resistance silicon diode D ₂ to D ₅ in the same manner for each R ₂ to R ₅ of _5, and the switch S ₂ to S ₅ is connected to a rechargeable battery of the present embodiment Configured as. Further, the charger in this case is configured to have a plunger capable of turning on / off the switches S _{1 to} S ₅ as in the embodiment of FIG.

When charging the rechargeable battery in this embodiment, after the rechargeable battery is mounted on the charger, a switch S ₁ to
With S ₅ turned on, each of the NiCd cells E _{1 to} E ₅ is _first discharged. During this discharge, the NiCd cell E
_The current supplied from each of _{1 to} E ₅ goes through the silicon diodes D _{1 to} D ₅ . This silicon diode has a characteristic that a current conducts in a forward direction when a voltage higher than a predetermined voltage is applied.

FIG. 4 is a graph showing the discharge state of the NiCd cell, showing the change in the battery voltage with the discharge time. A curve D represents a discharge state in the present embodiment, that is, a discharge state when the silicon diode is used, and a curve E shown by a broken line represents a discharge state when the discharge is performed without the silicon diode.

As shown in this graph, when the discharge time elapses and the remaining capacity of the NiCd unit cell decreases, the voltage sharply decreases at a certain point. Then, from this time point, when further discharging is performed without passing through the silicon diode, the voltage continues to drop as shown by the curve E, but even if the remaining capacity becomes 0, further discharging seems to continue. In some cases, it falls into the state of over-discharge.

Repeating this over-discharging may also shorten the life of or destroy the Ni-Cd battery as in the case of over-charging. For this reason, the charger is configured so that the discharge before charging is performed only for a predetermined time set according to the characteristics of the unit cell, or the user is instructed to do so. Over-discharge may occur.

On the other hand, in the case of discharging through the silicon diode, even if the voltage starts to decrease, FIG.
As indicated by the curve D in Fig. ₁ , the discharge operation ends at this point because the silicon diode becomes non-conductive near the offset voltage of the silicon diode (about 0.6 V in this case), and each nickel cadmium cell E ₁ ~ E ₅ maintains a predetermined voltage value (about 0.6 V in this case) shown in the graph,
It is possible to eliminate the variation in the remaining capacity and avoid over-discharge. Then, after the discharging is performed as described above, the switches S _{1 to} S ₅ inside the rechargeable battery are turned off by the plunger on the charger side, and the specific NiCd cell is overcharged by charging. You can avoid becoming.

As described above, in this embodiment, not only the same effects as those of the embodiments shown in FIGS. 1 and 2 described above are obtained, but also by connecting the silicon diode, it is possible to avoid over-discharge. It is something.

It is needless to say that the number of the single secondary batteries constituting the assembled secondary battery can be changed according to the equipment used and the like, and the present invention can be applied to secondary batteries other than the NiCad single battery. . In addition, the connection order of the load resistance, the switch, and the silicon diode in each embodiment of FIGS. 2 and 3, the shape of the power pack 1 that is the outer shape of the rechargeable battery, and the like can be changed according to various conditions. .

[0040]

As described above, the assembled secondary battery of the present invention is configured such that a load resistance and a switch are connected in series to each unit cell so that each unit cell can be discharged. , It became possible to charge the battery after eliminating the variation in the remaining capacity of each cell. As a result, it is possible to prevent the unit cell from being overcharged, and there is an effect that the life of the assembled secondary battery is not unnecessarily shortened. Further, in addition to the load resistance and the switch, a silicon diode is connected to prevent over-discharge, so that the original life of the assembled secondary battery can be secured more reliably.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an assembled secondary battery as an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an assembled secondary battery as another embodiment of the present invention.

FIG. 3 is a circuit diagram showing an assembled secondary battery as still another embodiment of the present invention.

FIG. 4 is a graph showing discharge characteristics of a single secondary battery.

FIG. 5 is a perspective view showing an assembled secondary battery as an embodiment of the present invention.

FIG. 6 is a circuit diagram showing an assembled secondary battery in a conventional example.

FIG. 7 is a graph showing charge characteristics of a single secondary battery.

FIG. 8 is a graph showing the self-discharge characteristics of a single secondary battery.

[Explanation of symbols]

1 Power pack E _{1 to} E ₅ NiCd cell T _{1 to} T ₆ terminal R _{1 to} R ₅ load resistance S _{1 to} S ₅ switch D _{1 to} D ₅ silicon diode

Claims (3)

[Claims] 1. A terminal is provided between each of a plurality of single secondary batteries connected in series, and each single secondary battery can be independently discharged between the terminals. A secondary battery characterized by. 2. A series circuit of a discharging impedance and a switch is connected to each of the plurality of single secondary batteries connected in series, and the single secondary batteries are independently provided by the series circuit. An assembled secondary battery, which is configured to be dischargeable. 3. The assembled secondary battery according to claim 2, wherein the discharging impedance is formed by a series circuit of a diode and a resistor.